According to a Washington Post report, the flight from Las Vegas to Kalispell, Mont., near Zinke's home in Whitefish, Mont., cost taxpayers $12,375. Commercial flights run daily between the airports and cost as little as $300.

Zinke also used private planes during a trip to the Virgin Islands, according to the Post.

Zinke had reportedly been in Las Vegas to give a speech to the city's hockey team, the Vegas Golden Knights.

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Heather Swift, a spokeswoman for the Interior Department, said the Zinke charter flights were approved by ethics officials and that private planes were only used when commercial flights were unavailable.

The Post report followed a Politico report that Zinke and his aides have taken multiple flights on private or military planes to go to events in his home state of Montana and between two Caribbean islands.

Swift told Politico that Zinke's other flights were booked after the department was unable to find commercial flights corresponding with the secretary's schedule and that they were all pre-cleared by ethics officials in the department.

Still, the revelation could pull Zinke into the expanding controversy surrounding the use of private and government aircraft by some Trump administration officials.